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<h3 class="section" id="Brief-Description-of-gcov-Data-Files"><span>10.4 Brief Description of <code class="command">gcov</code> Data Files<a class="copiable-link" href="#Brief-Description-of-gcov-Data-Files"> &para;</a></span></h3>

<p><code class="command">gcov</code> uses two files for profiling.  The names of these files
are derived from the original <em class="emph">object</em> file by substituting the
file suffix with either <samp class="file">.gcno</samp>, or <samp class="file">.gcda</samp>.  The files
contain coverage and profile data stored in a platform-independent format.
The <samp class="file">.gcno</samp> files are placed in the same directory as the object
file.  By default, the <samp class="file">.gcda</samp> files are also stored in the same
directory as the object file, but the GCC <samp class="option">-fprofile-dir</samp> option
may be used to store the <samp class="file">.gcda</samp> files in a separate directory.
</p>
<p>The <samp class="file">.gcno</samp> notes file is generated when the source file is compiled
with the GCC <samp class="option">-ftest-coverage</samp> option.  It contains information to
reconstruct the basic block graphs and assign source line numbers to
blocks.
</p>
<p>The <samp class="file">.gcda</samp> count data file is generated when a program containing
object files built with the GCC <samp class="option">-fprofile-arcs</samp> option is executed.
A separate <samp class="file">.gcda</samp> file is created for each object file compiled with
this option.  It contains arc transition counts, value profile counts, and
some summary information.
</p>
<p>It is not recommended to access the coverage files directly.
Consumers should use the intermediate format that is provided
by <code class="command">gcov</code> tool via <samp class="option">--json-format</samp> option.
</p>
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